Asymmetric BIS (indolestyryl) compound and high density recording media utilizing the same

ABSTRACT

An asymmetric bis(indolestyryl) compound. The asymmetric bis(indolestyryl) compound has formula (I):  
                 
         wherein A and B comprise benzene, naphthalene, or heterocyclic ring containing O, S, or N, R1 and R1′ are H, halogen atoms, C 1-5  alkyl, nitro, ester, carboxyl, sulfo, C 1-3  alkoxy, amine, alkylamine, cyano, C 1-6  alkylsulfonyl, or C 2-7  alkoxy carbonyl, R 2 , R 2 ′, R 3 , and R 3 ′ comprise H, C 1-6  alkyl, C 6-18  aryl, C 2-6  alkenyl, C 3-6  cycloalkenyl, or C 3-6  cycloalkyl, or C 3-6  cycloalkyl containing hetero atom, R 4  is H, hydroxyl, halogen atoms, or alkoxy, R 5  and R 5   1  comprise H, halogen atoms, C 1-5  alkyl, nitro, C 1-3  alkoxy, amine, cyano, C 1-6  alkylsulfonyl, or C 2-7  alkoxy carbonyl, n is 1˜18, Y is C(R 6 R 7 ), C 1-3  alkylamino or hetero atom, R 6  and R 7  are C 1-3  alkyl, and Z −  is an anion or an anionic organometallic complex. The invention also provides a high density recording medium utilizing the asymmetric bis(indolestyryl) compound.

BACKGROUND

The present invention relates to an indolestyryl compound, and more specifically to an asymmetric bis(indolestyryl) compound used in a high density recording medium.

With advances in information and multimedia generation, computer, communication, and consumer (3C) electronic products with increased recording density and capacity, microminiaturization and low cost are required to meet the flow of information. Currently, magnetic recording media have been replaced by high density optical recording media.

For optical recording media, improved recording density has been provided by, for example, reduction of wavelength of readout laser such as reduction from red light region to blue, or increase of number aperture (NA). Another important research topic, however, is modification of organic dye structures in optical recording layers. Research has endeavored to develop optical dyes with high solubility, strong absorption in visible light region, photostability, thermal stability, or simple synthesis.

Dyes of CD-R are not suitable for use in high density recording media such as DVD-R due to their different laser wavelengths, CD-R having 780 nm and DVD-R 650 nm. Additionally, related organic dyes in recording layers lack photostability, thermal stability, and simple synthesis, resulting in shorter recording times and higher costs. Thus, development of organic dyes providing improved optical characteristics of high recording media is desirable.

SUMMARY

The invention provides an asymmetric bis(indolestyryl) compound having formula (I):

wherein A and B are the same or different and comprise benzene, naphthalene, or heterocyclic ring containing O, S, or N, R₁ and R₁′ are H, halogen atoms, C₁₋₅ alkyl, nitro, ester, carboxyl, sulfo, C₁₋₃ alkoxy, amine, alkylamine, cyano, C₁₋₆ alkylsulfonyl, or C₂₋₇ alkoxy carbonyl, R₂, R₂′, R₃, and R₃′ are the same or different and comprise H, substituted or non-substituted C₁₋₆ straight chain or branched alkyl, substituted or non-substituted aryl, C₂₋₆ straight chain or branched alkenyl, C₃₋₆ cycloalkenyl, or substituted or non-substituted C₃₋₆ cycloalkyl, or C₃₋₆ cycloalkyl containing hetero atom, R₄ is H, hydroxyl, halogen atoms, or alkoxy, R₅ and R₅′ are the same or different and comprise H, halogen atoms, C₁₋₅ alkyl, nitro, C₁₋₃ alkoxy, amine, cyano, C₁₋₆ alkylsulfonyl, or C₂₋₇ alkoxy carbonyl, n is 1˜18, Y is C(R₆R₇), C₁₋₃ alkylamino or hetero atom, R₆ and R₇ are C₁₋₃ alkyl, and Z⁻ is an anion or an anionic organometallic complex, and wherein, when A=B, R₁ is not equal to R₁′ and when A≠B, R₁ is equal to R₁′ or not, and R₂ and R₃ or R₂′ and R₃′ are joined together or with a benzene to form a ring.

The invention also provides a high density recording medium comprising a first substrate, a recording layer formed thereon comprising the disclosed asymmetric bis(indolestyryl) compound, a reflective layer formed on the recording layer, and a second substrate formed on the reflective layer.

A detailed description is given in the following embodiments with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:

FIG. 1 is a cross section of a high density recording medium of the invention.

DETAILED DESCRIPTION

The invention provides an asymmetric bis(indolestyryl) compound having formula (I):

In formula (I), A and B are the same or different such as benzene, naphthalene, and heterocyclic ring containing O, S, or N, such as furan, pyrazine, pyrrole, pyrazole, pyridazine, pyridine, pyridone, pyrimidine, thiazole, thiophene, quinine, and isoquinine. R₁ and R₁′ comprise H, halogen atoms, C₁₋₅ alkyl, nitro, ester, carboxyl, sulfo, C₁₋₃ alkoxy, amine, alkylamine, cyano, C₁₋₆ alkylsulfonyl, or C₂₋₇ alkoxy carbonyl. When A=B, R₁ is not equal to R₁′, and when A≠B, R₁ is equal to R₁′ or not, R₂, R₂′, R₃, and R₃′ are the same or different such as H, substituted or non-substituted C₁₋₆ straight chain or branched alkyl, substituted or non-substituted C₆₋₁₈ aryl, C₂₋₆ straight chain or branched alkenyl, C₃₋₆ cycloalkenyl, or substituted and non-substituted C₃₋₆ cycloalkyl or C₃₋₆ cycloalkyl containing hetero atom. R₂ and R₃ or R₂′ and R₃′ may be joined together or with a benzene to form a ring. Substituted groups in R₂, R₂′, R₃, and R₃′ comprise halogen atoms, nitro, cyano, hydroxyl, carboxyl, ester, sulfo, sulfoate, or sulfamide. R₄ may conmprise H, hydroxyl, halogen atoms, or alkoxy. R₅ and R₅′ are the same or different such as H, halogen atoms, C₁₋₅ alkyl, nitro, C₁₋₃ alkoxy, amine, cyano, C₁₋₆ alkylsulfonyl, and C₂₋₇ alkoxy carbonyl. Y is C(R₆R₇), C₁₋₃ alkylamino or hetero atom, wherein R₆ and R₇ are C₁₋₃ alkyl. Z⁻ is an anion or an anionic organometallic complex such as halogen atoms, ClO₄ ⁻, BF₄ ⁻, PF₆ ⁻, BPh₄ ⁻, SbF₆ ⁻, tetracyano p-quinodimethane (TCNQ⁻), tetracyano ethylene (TCNE⁻), and benzene sulfonate, and n is 1˜18.

The asymmetric bis(indolestyryl) compound has an absorbing wavelength of about 400˜700 nm, an absorbing coefficient (ε) exceeding 10⁵, and a solubility exceeding 2% in organic solvent such as C₁₋₆ alcohol, C₁₋₆ ketone, C₁₋₈ ether, halide, and amide.

The asymmetric bis(indolestyryl) compounds provided by the invention comprise

The compound of formula (I) is prepared as follows. First, an asymmetric bis-indole compound such as

solvent such as ethanol or methanol, and benzaldehyde such as p-N,N-diethyl benzaldehyde or p-N,N-dihexyl benzaldehyde, are added to a flask and reacted at 80˜100° C. for 20˜24 hours. An asymmetric bis(indolestyryl) compound is prepared after extracting solvent. The asymmetric bis(indolestyryl) compound, solvent such as methanol or ethanol, and a metal salt are added to a flask and reacted at 80˜100° C. for 1˜2 hours. The metal salt comprises Li, Na, or K salt such as NaSbF₆ or NaPF₆. After cooling to room temperature and filtration, an asymmetric bis(indolestyryl) compound provided by the invention is prepared.

The invention also provides a high density recording medium comprising a first substrate, a recording layer formed thereon comprising the disclosed asymmetric bis(indolestyryl) compound, a reflective layer formed on the recording layer, and a second substrate formed on the reflective layer.

The first and second substrates are transparent substrates having trenches and comprise polyester, polycarbonate, or polyolefin. The recording layer has a thickness of about 50˜300 nm and comprises asymmetric bis(indolestyryl), cyanine dye or azo metal chelate compounds. The asymmetric bis(indolestyryl) compound and cyanine dye or azo metal chelate compounds have a weight ratio of about 100:0˜1:99. The reflective layer comprises Au, Ag, Al, Cu, Cr, or alloys thereof.

The high density recording medium has a reflectance of about 40˜60%, preferably 52%, a jitter of about 8.5˜10.5, preferably 8.7, and a modulation of about 0.6˜0.7, preferably 0.69. The high density recording medium comprises a Digital Versatile Disk-Recordable (DVD-R).

A method of fabricating a high density recording medium is further provided. A first substrate is provided and a solution containing an asymmetric bis(indolestyryl) compound and solvent is prepared simultaneously. The solvent may comprises C₁₋₆ alcohol, C₁₋₆ ketone, C₁₋₈ ether, dibutyl ether (DBE), halide, or amide. The C₁₋₆ alcohol comprises methanol, ethanol, isopropanol, diaceton alcohol (DAA), 2,2,3,3-tetrafluoropropanol (TFP), trichloroethanol, 2-chloroethanol, octafluoropentanol, or hexafluorobutanol. The C₁₋₆ ketone comprises acetone, methyl isobutyl ketone (MIBK), methyl ethyl ketone (MEK), or 3-hydroxy-3-methyl-2-butanone. The halide comprises chloroform, dichloromethane, or 1-chlorobutane. The amide comprises dimethyl formamide (DMF), dimethyl acetamide (DMA), or methyl cyclohexane (MCH). The solution is then coated on the first substrate and dried to form a recording layer, utilizing spin coating, vacuum deposition, spray coating, immersion coating, stick coating, fluid coating, printing coating, or tape coating, preferably spin-coating. Next, a reflective layer is evaporated on the recording layer. Finally, a second substrate is bonded to the reflective layer to form a high density recording medium. A protection layer may be coated on the reflective layer before the second substrate is bonded.

EXAMPLES Example 1 Preparation of Compound 1

0.75 g

0.4 g

and ethanol were added to a 50 ml flask with thermal reflux overnight. 0.95 g

was obtained. 0.95 g

ethanol, and 0.75 g NaSbF₆ were added to a 50 ml flask with thermal reflux overnight. After cooling to room temperature and filtration, 1.04 g compound 1 was prepared with yield of 89.4%.

Example 2 Preparation of Compound 4

2 g

1 g

and ethanol were added to a 50 ml flask with thermal reflux overnight. 2.85 g green

was obtained. 1.69 g

ethanol, and 0.63 g NaSbF₆ were added to a 50 ml flask with thermal reflux overnight. After cooling to room temperature and filtration, 1.46 g blue color compound 4 was prepared with yield of 83.5%.

Example 3 Preparation of Compound 5

2.52 g

2.29 g

and ethanol were added to a 50 ml flask with thermal reflux over night. 4.9 g

was obtained. 2.45 g

ethanol, and 1.15 g NaSbF₆ were added to a 50 ml flask with thermal reflux overnight. After cooling to room temperature and filtration, 1.68 g compound 5 was prepared with yield of 62.4%.

Six asymmetric bis(indolestyryl) compounds (compound 1˜6) were prepared, with absorbing wavelengths (nm) and absorbing coefficient (ε) as shown in Table 1. TABLE 1 Absorbing Absorbing Compound wavelength coefficient number Structure (nm) (ε) Compound 1

561 1.77 * 10⁵ Compound 2

561  1.5 * 10⁵ Compound 3

557 1.62 * 10⁵ Compound 4

556 1.97 * 10⁵ Compound 5

562 1.84 * 10⁵ Compound 6

564 1.71 * 10⁵

Example 4 Fabrication of High Density Recording Medium (1)

Referring to FIG. 1, a method of fabricating a high density recording medium is disclosed according to the following example, in which a polycarbonate first substrate 10 at a diameter of 120 mm and a thickness of 1.2 mm having trenches 12 at a depth of 130 nm and a width of 300 nm was provided. A solution (1.7 wt %) containing a compound 3 and 2,2,3,3-tetrafluoropropanol (TFP) was prepared simultaneously. Next, the solution was coated on the first substrate 10 by spin coating and dried at 80° C. for 5 min to form a recording layer 20. An Ag layer was then sputtered on the recording layer 20 to form a reflective layer 30 at a thickness of 200 nm. Finally, a second substrate 40 was bonded to the reflective layer 30 to form a high density recording medium. A UV resin was coated on the reflective layer 30 to form a protective layer of about 10 μm (not shown) before the second substrate 40 was bonded.

Example 5 Fabrication of High Density Recording Medium (2)

Referring to FIG. 1, a method of fabricating another high density recording medium is disclosed according to the following example, in which a polycarbonate first substrate 10 at a diameter of 120 mm and a thickness of 1.2 mm having trenches 12 at a depth of 130 nm and a width of 300 nm was provided. A solution (1.7%) containing a compound 4, cyanine dye of 0˜99% weight ratio, and 2,2,3,3-tetrafluoropropanol (TFP) was prepared simultaneously. Next, the solution was coated on the first substrate 10 by spin coating and dried at 80° C. for 5 min to form a recording layer 20 at a thickness of 200 nm. An Ag layer was then sputtered on the recording layer 20 to form a reflective layer 30 at a thickness of 200 nm. Finally, a second substrate 40 was bonded to the reflective layer 30 to form a high density recording medium. A UV resin was coated on the reflective layer 30 to form a protective layer of about 10 μm (not shown) before the second substrate 40 was bonded.

Reflectance, jitter, and modulation of high density recording media (1) and (2) were shown in Table 2. TABLE 2 Reflectance (%) Jitter Modulation High density 45.1 10.1 0.688 recording medium (1) High density 52.7 8.71 0.603 recording medium (2)

The results indicate that the high density recording media with modified recording layers of the invention provides better photoelectrical performance. Reflectance, jitter, and modulation of related products are 45%, 8.0, and 0.6, respectively. Additionally, these media also provide high recording sensitivity and high carrier-to-noise ratio (CNR).

While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements. 

1. An asymmetric bis(indolestyryl) compound having formula (I):

wherein A and B are the same or different and comprise benzene, naphthalene, or heterocyclic ring containing O, S, or N, R₁ and R₁′ are H, halogen atoms, C₁₋₅ alkyl, nitro, ester, carboxyl, sulfo, C₁₋₃ alkoxy, amine, alkylamine, cyano, C₁₋₆ alkylsulfonyl, or C₂₋₇ alkoxy carbonyl, R₂, R₂′, R₃, and R₃′ are the same or different and comprise H, substituted or non-substituted C₁₋₆ straight chain or branched alkyl, substituted or non-substituted C₆₋₁₈ aryl, C₂₋₆ straight chain or branched alkenyl, C₃₋₆ cycloalkenyl, or substituted or non-substituted C₃₋₆ cycloalkyl, or C₃₋₆ cycloalkyl containing hetero atom, R₄ is H, hydroxyl, halogen atoms, or alkoxy, R₅ and R₅′ are the same or different and comprise H, halogen atoms, C₁₋₅ alkyl, nitro, C₁₋₃ alkoxy, amine, cyano, C₁₋₆ alkylsulfonyl, or C₂₋₇ alkoxy carbonyl, n is 1˜18, Y is C(R₆R₇), C₁₋₃ alkylamino or hetero atom, R₆ and R₇ are C₁₋₃ alkyl, and Z⁻ is an anion or an anionic organometallic complex, wherein when A=B, R₁ is not equal to R₁′ and when A≠B, R₁ is equal to R₁′ or not, and R₂ and R₃ or R₂′ and R₃′ are joined together or with a benzene to form a ring.
 2. The asymmetric bis(indolestyryl) compound as claimed in claim 1, wherein A and B comprise furan, pyrazine, pyrrole, pyrazole, pyridazine, pyridine, pyridone, pyrimidine, thiazole, thiophene, quinine, or isoquinine.
 3. The asymmetric bis(indolestyryl) compound as claimed in claim 1, wherein substituted groups in R₂, R₂′, R₃, and R₃′ comprise H, halogen atoms, alkyl, alkyl halide, nitro, cyano, hydroxyl, carboxyl, ester, sulfo, sulfoate, sulfamide, morpholine, julolidine, or piperazine.
 4. The asymmetric bis(indolestyryl) compound as claimed in claim 1, wherein Z comprises halogen atoms, ClO₄ ⁻, BF₄—, PF₆—, BPh₄—, SbF₆—, tetracyano p-quinodimethane (TCNQ⁻), tetracyano ethylene (TCNE⁻), benzene sulfonate, or anionic organometallic complex.
 5. The asymmetric bis(indolestyryl) compound as claimed in claim 1, wherein the asymmetric bis(indolestyryl) compound comprises


6. The asymmetric bis(indolestyryl) compound as claimed in claim 1, wherein the asymmetric bis(indolestyryl) compound comprises


7. The asymmetric bis(indolestyryl) compound as claimed in claim 1, wherein the asymmetric bis(indolestyryl) compound comprises


8. The asymmetric bis(indolestyryl) compound as claimed in claim 1, wherein the asymmetric bis(indolestyryl) compound comprises


9. The asymmetric bis(indolestyryl) compound as claimed in claim 1, wherein the asymmetric bis(indolestyryl) compound comprises


10. The asymmetric bis(indolestyryl) compound as claimed in claim 1, wherein the asymmetric bis(indolestyryl) compound comprises


11. The asymmetric bis(indolestyryl) compound as claimed in claim 1, wherein the asymmetric bis(indolestyryl) compound has an absorbing wavelength of about 400˜700 nm.
 12. The asymmetric bis(indolestyryl) compound as claimed in claim 1, wherein the asymmetric bis(indolestyryl) compound has an absorbing coefficient (ε) exceeding 10⁵.
 13. The asymmetric bis(indolestyryl) compound as claimed in claim 1, wherein the asymmetric bis(indolestyryl) compound has solubility exceeding 2% in organic solvent.
 14. The asymmetric bis(indolestyryl) compound as claimed in claim 13, wherein the organic solvent comprises C₁₋₆ alcohol, C₁₋₆ ketone, C₁₋₈ ether, halide, or amide.
 15. A high density recording medium, comprising: a first substrate; a recording layer formed on the first substrate comprising an asymmetric bis(indolestyryl) compound as claimed in claim 1; a reflective layer formed on the recording layer; and a second substrate formed on the reflective layer.
 16. The high density recording medium as claimed in claim 15, wherein the first and second substrates are transparent substrates having trenches.
 17. The high density recording medium as claimed in claim 15, wherein the first and second substrates comprise polyester, polycarbonate, or polyolefin.
 18. The high density recording medium as claimed in claim 15, wherein the recording layer comprises cyanine dye or azo metal chelate compounds.
 19. The high density recording medium as claimed in claim 18, wherein the asymmetric bis(indolestyryl) compound and cyanine dye or azo metal chelate compounds have a weight ratio of about 1:99˜99.9:0.1.
 20. The high density recording medium as claimed in claim 15, wherein the reflective layer comprises Au, Ag, Al, Cu, Cr, or alloys thereof.
 21. The high density recording medium as claimed in claim 15, wherein the high density recording medium has a reflectance exceeding 45%, a jitter of about 7.5-10.5, and a modulation of about 0.6˜0.8.
 22. The high density recording medium as claimed in claim 15, wherein the high density recording medium comprises a High Density Digital Versatile Disk-Recordable (DVD-R). 